The present invention relates to instrumentation for spinal osteosynthesis systems.
When fitting a spinal osteosynthesis system in place, the surgeon is forced to modify the distance separating the two vertebrae receiving the osteosynthesis system. Moreover, when fitting this by an endoscopic route, the use of a conventional forceps called a distractor (used in cases where the vertebrae are to be spaced apart from one another) or called a contractor (used in cases where the vertebrae are to be brought closer to one another) is problematic or even impossible on account of its size. Furthermore, the endoscopy instruments have courses which are too short or they do not permit the application of sufficient forces to perform the operation of distraction or contraction.
Furthermore, the document DE 91 12 466 U discloses instrumentation with which it is possible to position two pedicle screws relative to one another. This instrumentation is made up of two arms interfacing with the pedicle screws and linked to each other by two displacement devices which each have two threads in opposite directions and engaging with the respective arms. The instrumentation as a whole is very voluminous, which means that it cannot be used in endoscopic surgery.
It is an object of the present invention to make available a device which permits distraction and contraction of two vertebrae while at the same time being able to be applied by an endoscopic route and being easy to use.
According to the present invention, this object is achieved by providing a distraction and/or contraction device for surgery of the spine, comprising connectors designed to be fixed to respective vertebral anchoring members, means for linking these connectors, and means for adjusting a distance comprising an assembly of pinion and endless screw.
Thus, the device makes it possible to perform distraction or contraction between two vertebrae in a simple way, while maintaining the applied displacement by a nonreturn effect without any intervention by the operating surgeon.
Advantageously, the means for adjusting a distance comprise a rod designed to link the connectors.
Advantageously, the rod is free both in translation and rotation on its own axis relative to one of the connectors.
Advantageously, the rod is free in rotation about its own axis relative to the other of the connectors.
Advantageously, the rod is free both in translation and rotation on its own axis relative to the other of the connectors with a helix of opposite direction.
Advantageously, the rod is immobilized in translation and in rotation on its own axis relative to one of the connectors.
Advantageously, the rod is free in translation on its own axis relative to the other of the connectors.
Advantageously, the pinion is rigidly integral with the rod.
Advantageously, the pinion forms a screw/nut link with the rod.
Advantageously, the device comprises linking means between the rod and the connectors, these linking means comprising the pinion.
Advantageously, the device comprises linking means between the rod and the connectors, these linking means comprising a block which forms an abutment for the translation and/or rotation movement of the rod relative to the connector on the axis of the rod.
Advantageously, the block has a polygonal cross section, preferably with four sides.
Advantageously, at least one of the connectors has a bifid hook delimiting a space designed to receive the rod and its means of linkage.
Thus, the device can be dismantled into small elements, thus facilitating its use by endoscopy and also its assembly.
Advantageously, the device is designed in such a way that when the block is received, one of the sides of the polygonal cross section of the abutment is able to come into contact with the bottom of the space of the bifid hook.
Advantageously, one of the connectors comprises a ring with a spherical face.
Advantageously, the connector comprises a chamber designed to receive the ring with rotation.
Advantageously, the connector comprises a locking means designed to immobilize the ring in rotation.
Advantageously, the locking means comprises a concave spherical face designed to come into contact with the spherical face of the ring.
Advantageously, one of the connectors is adjacent to the pinion and endless screw assembly.
Advantageously, the endless screw can be received with rotation in the connector.
Advantageously, the device additionally comprises an instrument, for maneuvering the endless screw, and designed to receive the endless screw with rotation.
Advantageously, the instrument comprises a bifid hook delimiting a space, designed to receive the rod and the pinion rigidly integral with the rod.
The invention also provides a spinal osteosynthesis system comprising two vertebral anchoring members and a distraction and/or contraction device according to the present invention.
Advantageously, one of the connectors is able to form a ball and socket link with the associated vertebral anchoring member.
Thus, the device can be placed on anchoring members with defective alignment and parallelism.
Advantageously, the ring is designed to be fitted on the vertebral anchoring member.
The invention also provides a surgical method intended to perform spinal osteosynthesis with the aid of such an osteosynthesis system comprising a distraction and/or contraction device according to the present invention: placing the anchoring members on the vertebrae, then placing the device on the anchoring members and adjusting the distance, then fitting the osteosynthesis system, then removing the device.